The use of two-dimensional exhaust nozzles on gas turbine engines is well known in the art. Such exhaust nozzles are described in U.S. Pat. Nos. 4,310,121; 4,690,329; and 4,763,840. The nozzles described in each of these patents is characterized as two-dimensional due to the nozzle having a roughly rectangular exhaust flow path defined by two laterally spaced apart sidewalls and two vertically spaced apart planar nozzle flaps. Due to the intense heat of the engine exhaust gas which contacts the planar nozzle flaps in the convergent section of the nozzle, these convergent flaps must be cooled to prevent life reduction, or failure, of the flap components.
In the past, attempts to cool the convergent flap have included using cooling air supplied to the the convergent flap to provide a combination of impingement cooling and film cooling of the convergent flap liner. In this scheme, the spent cooling air was exhausted through the liner into the exhaust gas flow to provide film cooling of the convergent flap liner, and film cooling of the divergent flap liner downstream. However, at certain engine operating conditions, the static pressure of the cooling air was found to be lower than that of the prevailing static pressure of the exhaust gas, causing aspiration of the hot exhaust gas through the liner and resulting in liner temperatures that exceeded liner material capabilities.
More recently, imperforate liners have evolved which eliminate the film cooling to avoid the aspiration problems of the prior art liners, yet still provide film cooling of the divergent flap liners downstream. These liners typically use a thermal barrier coating on the exhaust gas side or "hot side" of the liner, and rely on impingement cooling of the "cool side" of the liner to provide the required cooling. Although impingement cooling generally provides adequate cooling for most of the liner, under certain conditions the trailing edge segment of the liner may still experience liner temperatures that exceed liner material capabilities. In addition, the high temperatures and pressures of the exhaust gas tend to deflect the liner toward the planar flap to which it is attached, reducing the flow of coolant from the liner.
What is needed is a cooling system for the trailing edge segment which prevents liner temperatures from exceeding liner material capabilities, without significantly disrupting the film cooling of the divergent flap liner downstream.